It is a common practice to transport by ship a lot of containers put one upon another in a plurality of tiers. If containers are simply piled one upon another, they may fall owing to the rolling of ship. To prevent the fall of containers, upper and lower containers are usually coupled together by use of coupling devices.
As one example of such prior art coupling devices, there is known one which comprises a body having an upper portion adapted to be detachably fitted in an engaging hole formed in a bottom corner of the upper container, an insertion shank provided on the underside of the body and insertable into an engaging hole formed in a top corner of the lower container, and an engaging body provided on the underside of the insertion shank. After inserting the insertion shank into the engaging hole, the engaging body is provided to bring both ends of the engaging body, which protrude outwardly from both sides of the insertion shank, into engagement with the peripheral wall of an opening at the lower side of the engaging hole.
With this coupling device, a shaft provided on the top surface of the engaging body is inserted into an insertion hole formed in the body of the coupling device, a lever coupled to the shaft is inserted in a lever insertion hole opening to one side of the body of the coupling device and elongated in the transverse direction, and then the engaging body is pivoted by controlling the lever. This means that the lever has to be necessarily turned when coupling the upper and lower containers together. Thus the coupling of containers was an extremely troublesome task.
Moreover, there is a fear that the engaging body, which is held in an engaged position, might pivot to a disengaged position owing to rolling and vibration during transportation. Thus the reliability of coupling is low.